Electromagnetic motion imparting means and transportor system embodying the same

ABSTRACT

An electromagnetic device producing a mechanical action, as in a transporter system comprising a suspended car, or in an electric motor, includes a magnetizing assembly and a magnetized assembly adapted to move one with respect to the other. The magnetizing assembly comprises at least one magnetic circuit defining an air gap and provided with at least one inductor winding, the magnetized assembly, subjected to the action of the magnetizing assembly comprising at least one magnetic portion associated with at least one non-magnetic portion and being in part housed in the air gap of said magnetizing assembly. This latter comprises at least two electromagnetic units each comprising an air gap and disposed in line whereas said magnetized assembly comprises a number of separate magnetic sections at least equal to two, the pitch of which is different from that of the electromagnetic units of said magnetizing assembly, said magnetic sections being coupled together mechanically, separated by non-magnetic sections and constituting a series in line. The windings of said electromagnetic units are connected to a switch adapted to ensure their energization following a predetermined sequence, guiding means being provided so as to permit the displacement of the magnetic sections of said magnetized assembly in the air gaps of said electromagnetic units in a transverse direction relative to the lines of force in said air gap.

tutu-1g SR P198502 XR United States Patent [1 1 Barthalon et al.

I 54] ELECTROMAGNETIC MOTION IMPARTING MEANS AND TRANSPORTOR SYSTEMEMBODYING THE SAME Filed: April 28, 1970 Appl. No.2 32,774

Related US. Application Data Division 58 Ser. No. 697,089, Jan. 11,1968, abandoned.

[30] Foreign Application Priority Data Jan. 25, 1967 France ..67924llUS. Cl ..104/148 LM, 310/12 Int. Cl. ..B60l 13/00, H02k 41/02 Field ofSearch ..3l0/12, 13; 318/119-138; 68/23; 103/53; 160/331; 104/148 LM;246/182 R, 182 B, 182 C [5 6] References Cited UNITED STATES PATENTS12/1965 Roshala ..l04;3l0/l48 LM;12 2/1966 Smith et al ..l04/l48 LM2/1905 Zchden 2/1952 Holmquist 5/1968 Kwangho Chung ..l04/l48 LM 8/1969Reeks et a1 ..l04/l48 LM 2/1966 Smith et al "104/148 LM 51 Jan. 2, 1973Primary Examiner-Drayton E. Hoffman Attorney-Young & Thompson ABSTRACTAn electromagnetic device producing a mechanical action, as in atransporter system comprising a suspended car, or in an electric motor,includes a magnetizing assembly and a magnetized assembly adapted tomove one with respect to the other. The magnetizing assembly comprisesat least one magnetic circuit defining an air gap and provided with atleast one inductor winding, the magnetized assembly, subjected to theaction of the magnetizing assembly comprising at least one magneticportion associated with at least one non-magnetic portion and being inpart housed in the air gap of said magnetizing assembly. This lattercomprises at least two electromagnetic units each comprising an air gapand disposed in line whereas said magnetized assembly comprises a numberof separate magnetic sections at least equal to two, the pitch of whichis different from that of the lelectromagnetic units of said magnetizingassembly, said magnetic sections being coupled together mech ni all seara ted b non-m n etic secti ns nd constiluting a sei ies 1n ling. Thewi dmgs of said e ectromagnetic units are connected to a switch adaptedto ensure their energization following a predetermined sequence, guidingmeans being provided so as to permit the displacement of the magneticsections of said magnetized assembly in the air gaps of saidelectromagnetic units in a transverse direction relative to the lines offorce in said air gap.

.4". 9. 2m 40 Bre Figures PATENTEU JAN 2 I973 sum 01 0F 11 will.

MN RN Arm 5.

PATENTED A 2% 3,707,924

SHEET 03UF 11 6 05mm Ma/leoux PATRICK Warsaw PATENTEDJAM 21m SHEET 0? or11 Away/wk:

ELECTROMAGNETIC MOTION IMPARTING MEANS AND TRANSPORTOR SYSTEM EMBODYINGTHE SAME This application is a division of copending applica- 5 tionSer. No. 697,089, filed Jan. ll, 1968, now abandoned.

The present invention relates to an electromagnetic device capable ofproducing a mechanical action, as in transporter systems comprisingsuspended cars, or in electric motors, or the like.

This device is of the kind comprising a magnetizing unit and amagnetized unit which are movable one with respect to the other, themagnetizing unit comprising at least one magnetic circuit defining anair gap and provided with at least one field winding, while themagnetized unit which is subjected to the action of the magnetizing unitcomprises at least one magnetic section associated with at least onenon-magnetic section, and it is housed in part in the air gap of themagnetizing unit In particular, one of the units may be fixed, in whichcase the other may be associated with any device for receivingmechanical power.

Linear or rotary electric motors are already known which utilizepolyphase electric current and work by conversion of electro-magneticenergy to mechanical energy, and more precisely by the effect ofmagnetic induction generated by the field assembly in the armatureassembly.

The practical construction of linear motors of this type has seriousinadequacies: the controls of speed, acceleration and braking are notsatisfactory, the armature has a considerable mass and its conductivitymust be high, which necessitates the use, whenever the armature is long,of large quantities of copper or aluminum which are particularlyexpensive metals. Finally, the existence of a relative slip between thefield and the armature aggravates the problem presented by the controlof movement, and prevents the development of a large force at lowtranslation speeds.

Certain forms of linear electric induction motors permit the armature tobesupportedwith respect to the field or vice-versa andconstitute anelectromagnetic suspension, but this necessitates a power per unit ofweight which is too high to be utilizable in practice.

Another type of linear electric motor already described comprises asuccession of cylindrical windings surrounding a magnetized assemblysliding along the axis of the unit: however, the movement generated canthen only be transmitted by the extremity, which limits thepossibilities of application. The power/weight ratio is low and the unitpower is limited. The control of the movement and speed necessitatescomplicated and expensive switching and relay arrangements, since theair-gap is not precisely defined; the force varies considerably with theposition of the magnetic cores and the impulses received by themovingsystem are not well defined in time and in space.

Finally, amongst the rotary induction motors, the polyphase asynchronousmachines can only operate in a narrow range of speeds of rotation, andonly have a moderate starting torque, contrary to the requirements ofnumerous applications. Rotary direct-current motors do actually complywith the requirements, but these are of expensive construction since thefield and the armature must both be wound. Furthermore, the rotor cannotbe fixed in a pre-determined position.

The foregoing machines employ two well-known physical laws:

The so-called electrodynamic machines utilize the action of a field on acurrent;

in the others, the displacement of the moving system is parallel to thefield lines, and following the law of magnetic attraction, the forcevariation is inversely proportional to the square of the displacement.

The devices which form the object of the present invention make use of adifferent physical law, namely the fact that if there is established ina first element an electromagnetic circuit supplied at constant currentand closed by an air-gap in which is arranged a second elementcomprising a magnetic tooth, the edges of which are arrangedtransversely with respect to the flux, the attraction is very low whenthe tooth is out of the air-gap, but increases abruptly at the momentwhen the edge of the tooth passes into the air-gap, and then remainssubstantially constant, in spite of the displacement, until the conversephenomenon takes place. Under these conditions, the attraction is infact substantially proportional tothe variation of magnetic permeanceper unit displacement.

The present invention thus employs this particular law of force in orderto overcome the abovementioned difficulties and disadvantages, for thepurpose of con-' structing machines in which the force, thedisplacement, the speed and the acceleration of the magnetized unit withrespect to the magnetizing unit can be controlled in an accurate manner,whether the speed is in- 5 creasing or decreasing. Another object of theinvention is to obtain a particularly low mass for one of the two units,which is particularly advantageous in the case of linear electrictraction motors, in which the fixed portion is long, and of rotarymotors with high speeds of rotation, in which the rotor must be capableof withstanding large centrifugal forces.

, Another object of the invention is to obtain rotary motors with highstarting torques and variable speed of rotation over a wide range, thesemotors having furthermore a low production cost.

According to the invention, the electromagnetic device of the kinddefined above is characterized in that the magnetizing assemblycomprises at least two electromagnetic units, each comprising an air-gapand arranged in line, in that the magnetized assembly comprises a numberof separate magnetic sections at least equal to two, the pitch of whichis different from that of the electromagnetic units of themagnetizingassembly, these sections being mechanically coupled together, separatedby non-magnetic sections and forming a line; in that the windings of theelectromagnetic units are connected to a commutator ensuring theirexcitation following a predetermined sequence; and in that guiding meansare provided to permit the displacement of the magnetic sections of themagnetized assembly in the air-gaps of the electromagnetic units in atransverse direction relative to the lines of force in the said air- S PA particular, one of the two parts, the magnetized assembly, has a lowweight and a high power/weight ratio A device of this kind hasappreciable advantages. In

and its cost is small since it is not bulky and is made of cheapmagnetic material. The starting force is very high. The controls of theposition of the moving system, of its speed and acceleration, positiveor negative, are easily effected by acting on the electric impulseswitch.

The pitch of the electromagnetic units of the magnetizing assembly,measured along the axis of relative displacement of the two assembliesis preferably constant, but is different from the also constant pitch ofthe magnetic sections of the magnetized assembly. In particular, theaxial length corresponding to N pitches of one of the assemblies, andespecially of the magnetizing assembly, may be equal to the length of (Nl pitches of the other assembly, where N is a whole number.

This arrangement produces a uniform driving effort.

Depending on the applications, the magnetizing assembly and themagnetized assembly may extend in parallel rectilinear or coaxialcircular directions, or finally along any curvilinear directions, themoving system being then constituted by an in-line series of articulatedelements.

According to an advantageous feature of the invention, the devicecomprises means for regulating the starting and end instants of theelectric impulse supplying an electromagnetic unit, these means beingoperated as a function of at least one of the following parameters:position, speed, acceleration of the moving system with respect to thefixed system.

In particular, the device may advantageously comprise a detector of therelative position of a magnetic section and an electromagnetic unitwhich cooperates therewith, this detector being itself preferablyadjustable in position with respect to the assembly on which it iscarried enabling the electric impulse to be initiated or interrupted atan adjustable pre-determined position. This detector may beadvantageously combined with a device introducing, with a variable phaseaccording to the desired conditions of operation, this detection signalin a device which modulates the electric impulses. This combination ofregulating means having very great flexibility, makes it possible toensure precise control of the movement, the force, the speeds and theaccelerations, and furthermore ensures optimal efficiency.

According to another outstanding aspect of the invention, provision ismade to utilize the device in question as an effective system ofelectromagnetic suspension of one of the assemblies with respect to theother. A suspension of this kind represents a considerable economy ofmeans per unit of lifting force, with respect to other knownsuspensions. In fact, when an electromagnetic circuit is excited by anelectric impulse, a slight relative displacement of the magnetizing andmagnetized assemblies in a direction which is simultaneously normal tothe direction of movement and to that of the lines of force in theair-gap (namely a vertical downward direction) creates a large restoringforce on the magnetic section in the air-gap (namely an upward force),and this does not involve a considerable consumption of additionalenergy.

The industrial constructions which will now be described show that,depending on the application, the force applied by the magnetizingassembly may only cause a small displacement of the moving assembly,such as is the case in machines producing a vibratory movement. Thedevice may also produce a resultant movement of medium amplitude (as isthe case for pumps and compressors) or a movement of large amplitude(the case especially of conveyors of any kind: industrial conveyors,trains, etc.

In applications for which a large travel is required, it may beadvantageous to provide a fixed magnetized assembly and a movingmagnetizing assembly, and conversely for applications requiring a smalltravel. The various forms of construction of the invention vary betweentwo extreme cases: a machine in which the magnetized assembly comprisestwo magnetic sections successively attracted into the air-gaps of alarge number of electromagnetic circuits, and conversely a machine inwhich a large number of magnetic sections forming the magnetizedassembly are attracted successively into the air-gaps of two consecutiveelectromagnetic units. In the long-travel machines, if a small number ofelectromagnetic units is employed, a large number of magnetic sectionsis necessary for the magnetized assembly and vice-versa.

A remarkable special case of the long-travel construction is that inwhich the movement is rotating and there is thus obtained a rotary motorhaving the advantageous characteristics specified above, and inparticular a great aptitude for operation at high torque, at variablespeed and at high speed of rotation.

The electromagnetic device in accordance with the invention constitutesa driving machine which can be used over a large field of applicationsand especially in the case of the following apparatus:

Devices for lifting, or braking during lowering, with a linear movement,for lifts, lifting trucks, extraction of boring rods, pile-drivingequipment;

Sliding control devices, especially for doors, shuttles,

machine carriages;

Propulsion and braking devices for transport or handling means forpassengers, goods or equipment, comprising guided vehicles such as:trains, trolleys, launching catapults for aircraft or rockets, toys;

Actuating motors giving considerable power, for example for drivingtools for cold-forging metals by percussion or broaching tools;

Driving motors for alternating machines at relatively low speed andlarge travel, such as pumps and compressors;

Driving motors for devices of the chain type for caterpillar tractors,conveyors, bucket dredgers, etc.;

Driving motors for rotating machines such as cranedriving tables ordrilling platforms, vehicle wheels and more generally rotary machinesrequiring a high torque at low speeds, accurate control, a very widerange of speeds and a rotor having a low weight and low inertia;

Torque or force limiting or transmitting devices;

clutches;

Transmission to a distance of angles of rotation or lineardisplacements, remote recording, remote synchronization, servo-controls.

Further particular characteristics of the invention will be brought outin the description which follows below.

In the accompanying drawings, given by way of nonlimitative examples,there have been shown various industrial constructions according to theinvention.

FIG. 1 is a general perspective diagram of the device according to theinvention.

FIG. 2 is a view in cross-section taken along the line Illl of FIG. 3,of a first industrial construction relating to an actuating device.

FIG. 3 shows a cross-section taken along the line IIIIII of FIG. 2.

FIG. 4 is a cross-section taken along the line IVIV of FIG. 2.

FIG. 5 shows to a larger scale a detail of the crosssection along theline VV of FIG. 2.

FIG. 6 shows diagrammatically an immobilizing device for the movingelement of the first construction.

FIG. 7 is a transverse section of an alternative form of the firstconstruction, constituting an electromagnetic suspension.

FIG. 8 is a plan view from above of a magnetizing as sembly forming aconveyor.

FIG. 9 is a view to a larger scale of the above conveyor incross-section along the line IXIX of FIG. 8.

FIG. 10 is a side view of the magnetized assembly assumed to beisolated.

FIG. 11 is a transverse section of a lifting device for a vehicle.

FIG. '12 is a diagram of an electronic switching system of impulsesutilizable for the previous constructions.

FIG. 13 is a view in side elevation taken along the section XIIIXIII ofFIG. 14, showing an industrial construction intended for vehicletraction.

FIG. 14 is a cross-section taken along the line XIV XIV of FIG. 13.

FIG.15 is a section taken along the line XVXV of FIG. 13.

FIG. 16 shows the diagram of the electrical supply for the device ofFIGS. 13 to 15. i

FIG. 17 is a transverse section along the line XVII XVII of FIG. 18,showing an alternative form of the previous construction applied towall-effect vehicles.

FIG. 18 is a cross-section taken along the line SVIIIXVIII of FIG. 17.

FIG. 19 shows a detail of the cross-section XIX- XIX of FIG. 18.

FIG. 20 is a view in longitudinal section taken along the line XXXX ofFIG. 21, of a motor with a reciprocating movement.

FIGS. 21 and 22 are views in cross-section along the line XXL-XXI andXXII-XXII of FIG. 20.

FIG. 23 is a view in elevation of the cross-section XXIII-XXIII of FIG.24, showing another industrial construction intended for driving amember in rotation.

FIG. 24 is a cross-section taken along the line XXIV-XXIV of FIG. 23.

FIG. 25 shows diagrammatically the method of supplying the windings ofthe device of FIGS. 23 and 24.

FIG. 26 is a cross-section along the line XXVI- XXVI of FIG. 27, showingthe application of the invention to the construction of a micro-motor.

FIG. 27 is an axial cross-section along the line XXVII-XXVII of FIG. 26.

FIGS. 28 and 29 are detail explanatory diagrams concerning the startingsystem.

FIGS. 30 and 31 are diagrams of electrical supply devices.

FIG. 32 is a partial view of an alternative form of construction of themagnetized assembly of the above micro-motor, following the sectionXXXIIXXXII of FIG. 33.

FIG. 33 is a partial view in transverse section of an alternative formof construction of the magnetizing circuit.

FIG. 34 is a diagrammatic view in cross-section along the lineXXXIV-XXXIV of FIG. 35 of a motor with mechanical self-commutation.

FIG. 35 is a cross-section along the line XXXV- XXXV of FIG. 34.

FIG. 36 shows an alternative form with electrical self-commutation,taken along the line XXXVI XXXVI of FIG. 37.

FIG. 37 is a cross-section along the line XXXVIl- XXXVII of FIG. 36.

FIG. 38 is a diagram showing the electric switching device of theconstruction of FIGS. 36 and 37.

FIG. 39 is an explanatory diagram.

FIG. 40 is a diagram of a supply circuit.

There will first be described, with reference to FIG. 1 of theaccompanying drawings, a simplified construction of the device accordingto the invention.

This device is intended to produce a mechanical action (development of adriving or static force) and comprises essentially a magnetizingassembly 1 including at least two electromagnetic units 2 forming aseries. Each unit 2 comprises a magnetic circuit 3 having an air-gap 4and carrying a magnetizing winding 5 which creates a magnetic flux inthe said air-gap.

The device further comprises a magnetized assembly 6 including at leasttwo sections 7 of magnetic material (that is to say having a magneticpermeability greater than 1). The sections 7, the number of which isfurthermore different from that of the electromagnetic units 2, arecoupled mechanically to each other, arranged in line and separated bynon-magnetic sections 8 (for example of air).

The relative mechanical couplings of the assemblies 1 and 6 are suchthat a relative displacement may take place between them, thisdisplacement being effected in the air-gaps 4, in a substantiallytransverse direction with respect to the lines of force of the magneticflux created in these air-gaps.

The windings 5 of the electromagnetic units 2 are supplied from a source13 of electrical impulses through a commutator 14 which distributesthese impulses cyclically between the various windings 5.

The device may also comprise a system 15 for modulating the impulses,acting on the commutator l4 and controlled in turn simultaneously by theorders and operating data inscribed in a recording system 12, and by aunit 9 connected to a detector 10 of the position of the magnetizedassembly 6.

Means may further be provided for determining a preferential directionof displacement of the magnetized assembly 6.

In operation, the windings 5 of the magnetizing assembly 1 receivesuccessive electric impulses through the commutator 14 in such mannerthat the magnetic flux is established in at least one of the air-gaps 4at the moment when one of the magnetic sections 7 of the magnetizedassembly 6 has reached the entrance of this air-gap. The section 7 isthus attracted and tends to take up the position of minimum reluctancein the airgap 4. When this condition is reached, or during the course ofthe previous movement, a new circuit 3 is excited and attracts anothersection 7 at the moment or time when this latter also reaches theentrance of its air-gap, and so on.

Apart from special geometric relations which may be established betweenthe pitches of the air-gap 4 and those of the sections 7 in order thatone of these sections may be at the entry of an air-gap 4 when the othersection is located in this air-gap, for the purpose of permitting thesystematic and sequential development of a driving attraction, theinvention provides means for acting on the amplitude, the duration andthe phase of the impulses from the commutator 14 in order to provide aregulation, especially of the acceleration or the speed of themagnetized assembly 6.

The general features which have been specified above will now bedetailed and illustrated with reference to the description of theparticular applications of the invention.

The first particular construction of the invention illustrated in FIGS.2 to relates to a linear actuating device constituting a semi-staticdriving machine with controlled displacement. This device comprises aframe 21, on which is mounted the magnetizing assembly formed by asuccession of electromagnetic units 22, five in number in the caseselected. Each unit 22 comprises a magnetic circuit 23 formed by anassembly of magnetic laminated sheets, stamped out to the shape of a C.The interrupted arm thus forms a parallelepiped air-gap 24, between thetwo poles 25.

The circuits 23 are retained by a transverse bar 32 arranged in theircentral portion and fixed to the frame 21 by screws 33. The bar 32, ofnon-magnetic metal has a U-shaped section as shown in FIG. 5, and it isbor-.

dered by lugs 26 slotted with a bevel at the level of the poles 25similar to a rack, which ensures an absolutely firm fixing of the units22.

On each of the lateral branches of the circuits 23 are mounted themagnetizing windings 28 which, for the same unit, are supplied in phasefrom a source of direct-current 36, through a switch 39, a potentiometer39a. and a rotary switch 37, the rotating contact 38 of which is drivenby a motor 301 with two directions of rotation and variable speedregulated by the operator. This device could furthermore be replaced bya manually-operated crank-handle.

Each winding 28 of the electromagnetic unit 22 is connected to one ofthe terminals 37a, 37b, 37c, 37d and 37e of the rotary switch 37. Therotating contact 38 simultaneously establishes contact with several ofthe said terminals, as will be described later. The potentiometer 39aprovides a regulation for the power of the impulses and therefore of theforce applied on the moving element.

The magnetized assembly 27 is composed of a flat strip of magneticmaterial having a substantially parallelepiped shape, adapted to theair-gaps 24 and to the free space provided between the lugs 26 of thebar 32. The assembly 27 has a succession of magnetic sections formed byteeth 30 produced by cutting-out and forming a toothed rack. Thenon-magnetic sections arranged between the teeth 30 are constituted byblocks 31, of plastic material for example, which restore theparallelepiped shape of the strip and ensure the continuity of theguiding surface.

The assembly 27 thus constituted is slidably mounted axially on the bar32 between the poles 25 of the electromagnetic units 22.

The clearance between the magnetized assembly and the poles remainspractically constant over the greater part of the travel, due to thefact that the magnetic fields in the air-gaps 24 are transverse withrespect to the movement. The magnetized assembly 27 is guided in itsdisplacement by the lugs 26 of the bar 32, the play in this guidingaction being substantially twice as small as that existing between theelements 27 and the poles 25. The element 27 is coupled to theutilization device by a crank-arm 34 by means of an articulation shaft35. The friction of the element 27 with the bar'32 and the lugs 26 canbe reduced by employing self-lubricating materials 303 for the parts incontact (plastic material, non-magnetic alloy, for example) (see FIG.5).

In order to ensure the effective operation of the actuating device, thefollowing particular relations are preferably provided for theassemblies 22 and 27:

The parallelepiped shape of the air-gap 24 is such that its sectionperpendicular to the flux approximates to that of a square, the side ofwhich is larger than the thickness of the air-gap in the direction ofthe flux. I

Theaxial length of the non-magnetic sections 31 is slightly greater thanthe length of the poles 25 relative to the direction of the movement Lor M, and their height is slightly greater than that of the poles 25.

The axial length of the magnetizing assembly corresponding to N pitches(the pitch being the axial length of a pole plus the distance separatingtwo poles) is equal to that of (N 1) pitches of the magnetized assembly.1

The number of electromagnetic units is odd. Thus, in

the present embodiment, 5 pitches of the electromagnetic units 22 occupythe same axial length as 6 pitches of the magnetic sections 30.

This value of the pitch makes it possible to obtain a high proportion ofelectromagnetic units 22 which are active at any particular moment,while at the same time having an attraction in the opposite directionwith respect to the desired direction of movement having a value assmall as possible on the magnetized assembly 27. To the same end, it isprovided that the axial length of the non-magnetic sections 31 of themagnetized assembly 27 is greater than that of the magnetic sections 30in the proportion of 5 to percent. The spacing between theelectromagnetic units is thus fixed by all the foregoing points.

To the magnetized element 27 there may advantageously be added asolenoid-brake 40 (FIG. 6) intended to prevent any relative movementbetween the magnetizing assembly 22 and the magnetized assembly 27 whennone of the windings 28 is excited. When stationary, the magnetizedassembly 27 is gripped by two mechanical jaws 41 by the action ofsprings 42 applying a force in opposition to that of releaseelectromagnets 43, the sliding cores 302 of which are fixed to the jaws41. When theswitch 39 is closed, the jaws 41 move away from the element27 due to he attraction effect of the electromagnets 43 on the cores302.

The differential spacing of the electromagnetic units 22 and themagnetic sections 30 of the magnetized assembly 27 provides thefollowing operation: when one of the magnetic sections 30a is exactlybetween the poles of one of the electromagnetic units 22a, anothermagnetic section b of the magnetized as sembly is partially between thepoles of the following electromagnetic unit 22b, while the magneticsection 30c is ready to pass into the electromagnetic unit 22c and themagnetic section 30d is half-way between the units 220 and 22d.

The rotary switch 37 is arranged with respect to the fixed contacts 37a,37b, 372, in such manner that for this position of the element 27, theelectromagnetic unit 22b is excited, so that the magnetic section 30b isattracted in the direction L between the poles of this section. At theend of this movement, the section 30c is partially engaged in theelectromagnetic unit 22c, and the electromagnet unit 220 is then excitedinstead of the electromagnetic unit 22b, so that the movement of themagnetized assembly 27 in the direction L may continue.

Thus, the excitation in sequence of the electromagnetic units 22produces a movement of the magnetized assembly in the same direction asthe order in which these units are excited. Under these conditionshowever, it will be observed that only one of the electromagnetic unitsis excited at a given instant, so that the power/weight ratio of thesystem does not have its maximum value. In order to remedy this, theinvention provides for the simultaneous excitation of a secondelectromagnetic unit 22 as follows:

The rotating contact 38 of the switch 37 is arranged in such manner asto connect continuously two of the terminals such as 37a and 37b to thesource 36, and to establish contact with a fresh terminal 370 at theexact moment when it breaks the contact with the terminal 37a which itleaves behind.

Under these conditions, the magnetized element 27 being in the positionshown in FIG. 3, the unit 22a which supplies no driving force is notexcited, whereas the units 22b and 22c are excited simultaneously. Whenthe section 30b has come into the air-gap 24 of the unit 22b, thecorresponding winding 28 is de-excited in turn to the benefit of thewinding of the following unit, and so on. A reverse order of switchingis utilized in order to obtain a movement of the magnetized assembly 27in the opposite direction.

Rotation of the contact 38 thus controls the position, the direction,the movement and the acceleration of the moving magnetized element 27.The potentiometer 39a permits the regulation of the force applied in theaxial direction by this magnetized assembly 27 which, by means of thecrank-arm 34 communicates the movement and the force of the actuatingdevice to the member which is to be driven. This latter may equally wellbe a sliding door, a control device for a machinetool, or an aircraftcontrol device. The device considered can also be employed in place ofrotary electric motors with reduction gearing and worm-screws or toothedracks.

In certain applications of this embodiment, it is essential that themovement under load of the mag- This can be effected by various means,such as: magnetic sections having a sinusoidal profile, magneticsections having a slightly variable thickness and a permeability lessthan that of the circuit, lamination of this latter perpendicular to themovement, air-gap with a lightly variable thickness, switching de-phasedwith respect to the passage into and out of the air-gap, and moregenerally by any means controlling the increase of flux at the beginningof the introduction of a magnetic section 30 into the air-gap. There isthus obtained simultaneously an optimum efficiency and an easier controlof the movement.

By way of an alternative form, the present invention provides anactuating device of the foregoing type to ensure at the same time thepropulsion and also the lifting of a driven element. This embodiment isillustrated in FIG. 7, in which there is seen at 45 the driven elementwhich is to be simultaneously displaced and held in suspension. To thisend, the element 45 is attached by slings 46 to the magnetized assembly27 similar to that described above, but which is in this case locatedbelow the units 22 of the magnetizing assembly, itself fixed to thelower part of a fixed support 47 such as a ceiling or framework. Theweight of the element 45 tends to pull the magnetized assembly 27downwards and to pull the magnetic sections 30 out of the air-gaps 24,which creates restoring forces increasing rapidly with the verticaldisplacement. These forces finally counterbalance the weight of theelement 45. An additional lifting force may be obtained by joiningtogether the magnetic sections 30 by a transverse magnetic piece 48.

In order that the lift forces may be well distributed over the length ofthe magnetized assembly 27 it is provided to employ at least twomagnetizing assemblies, adequately spaced apart. The lift force isproportional to the axial length of the magnetic sections or teeth 30,while the propulsion force is proportional to the height of these teeth.Flanges or angle-iron sections 4, continuous over the whole length ofthe device and located below the element 27 prevent the latter fromfalling in the event of a failure of current supply.

In the foregoing devices, the switch 37 and the potentiometer 39aprovide a precise control of the actuating device and especially of itsposition, of the direction of movement, of the speed and theacceleration of the driven element. The driving force for starting-up islarge. The moving system may be held stopped in any position, even onload. The direct transmission of electromagnetic energy to themagnetized assembly 27 serving as an actuating slide results in a verysimple unit having no intermediate transmission element. The bulk of themagnetized assembly 27 is small and its construction of magnetic metalresults in a very low cost. By virtue of a magnetic play, substantiallygreater than the mechanical play and practically constant, and due tothe rules for dimensioning and switching indicated above, the force onthe moving magnetized element can be made practically constant for agiven current. The displacement is thus effected without appreciableshocks and there is no sticking effect on the poles.

A prototype machine in accordance with FIGS. 2 to 5 has been built andtested. Its characteristics are as follows:

Axial length of poles 19 mm.

Distance between poles 30 mm. Height of poles mm. Axial length ofmagnetized sections 19 mm. Axial length of non-magnetic sections 22 mm.Axial length of magnetic assembly 600 mm. Number of electromagneticunits 5 Total weight of magnetizing assembly 2.5 kg. Supply voltage 12volts Power absorbed 100 watts Resistance of each winding l.40 ohmsNumber of turns 2 X 2l0 Average force 2.5 kg.

Mechanical commutator.

The following operational results were obtained during the tests:

Maximum linear speed 2 m./sec. Pulsation speed obtained with alternatingcurrent for a travel of 100 mm 2 cmJsec. Maximum slope climbed by themagnetizing assembly forming a trolley 80% Maximum force of magneticlift: 3,700 g.: 100 37g.lwatt.

An alternative form of construction of the conveyor device of FIG. 7,intended to permit of movement over a curve, is shown in FIGS. 8 to 10.In this embodiment two magnetized assemblies 27a, 27b are provided, eachconstituted by an articulated assembly of magnetic sections 260 formingsuccessive castellations in which are interleaved non-magnetic sections261, also in the form of castellations which have an arrangementreversed with respect to the preceding. The sections 260 and 261 form inpairs substantially rectangular plates joined to each other by hingesthrough which pass the pivotal shafts 262. On each of these plates areprovided guiding shoes 263. The assemblies 27a, 27b each carry asupporting rod 46a, 46b, and these two suspension rods are coupledtogether by a swing-bar 264 which carries a lifting hook 265.

The magnetizing assembly constitutes a continuous supporting track witha curvilinear outline (FIG. 8) formed by a succession of electromagneticunits 22 each comprising a C-shaped circuit 23, as in the case of FIG.7, fixed to the support 47, and in theair-gap 24 of which can circulatethe magnetized assemblies 27a, 27b. In this case it is provided howeverto mount the magnetizing windings 28 on the horizontal limbs of thecircuits 23 and in the vicinity of the air-gaps 24. Above thepole-pieces 25 are arranged continuous friction bands 266 with which theshoes 263 are in contact. At the lower part of these pole-pieces arearranged guiding and safety angle-irons 49, by which the lower shoes 263are supported. The articulation axes 262 permit the assemblies 27a, 27bto follow the curves.

The units 22 are supplied with current in pairs, the correspondingwindings of the same pair being separated by a distance whichcorresponds to that separating the homologous sections 260 of theassemblies 27a, 27b.

The actuating device provided thus constitutes a particularly simpleelectromagnetic suspension .having a high power/weight ratio and lowfriction, the trajectory of which may have any desired form in space.

In the constructions which have just been described, the magnetizedassembly is moving and the magnetizing assembly is fixed, but thisarrangement may be reversed without departing from the scope of theinvention, especially in the cases where, for reasons of practicalconstruction, it is preferable to keep the magnetized assemblystationary and to cause the magnetizing assembly to move by attachingthe driven element 45 to this latter.

A version of this kind is shown diagrammatically in FIG. 11. Theconveyor comprises a magnetized assembly 250 fixed to the lower part ofthe support 47 and which comprises, as previously, a succession ofmagnetic and non-magnetic sections, such as 251. The magnetizingassembly 252 comprises a series of electromagnetic units 253 in line,fixed to the upper part of a vehicle 254 and playing simultaneously theparts of lifting and propulsion motors. Each unit 253 comprises inparticular two windings 267 located in the vicinity of the poles 268. Aspreviously, supporting angle-irons 269 prevent the fall of the vehicle254 in case of interruption of the current by coming to rest on awidened portion of the magnetized assembly 250.

The rotary switch 37 of FIG. 3, intended to ensure the sequentialswitching of the current supply to the electromagnetic units 22 may,according to a preferred embodiment of the invention shown in FIG. 12,be replaced by a static electronic device, in particular withthyristors.

More precisely, this device comprises a thyristor 51 assigned to eachwinding 28. The thyristor 51 is connected between the conductor 50acoupled to the negative pole of the source 36 and one of the terminalsof the winding 28 concerned, the other terminal of which is connected tothe positive pole of the source 36 by the conductor 50b.

The trigger of each thyristor 51 is controlled by an electronic gate 52of the AND type, of which one of the inputs is connected to an impulsegenerator 53 and the other input to a routeing contact 54. The fixedstuds of the contact 54 terminate respectively at the output circuit ofthe preceding thyristor 51 and of the following thyristor 51.

It can thus be seen that the control gate 52b of the thyristor 51b isconnected to the contact 54b, the fixed studs of which terminaterespectively at the outputs of the thyristor 51a and of the thyristor51c.

Condensers 55 are connected between the corresponding conductors of thewindings 28, two by two, following a circular permutation, and diodes 56are connected in parallel with each winding 28, their cathode beingcoupled to the positive pole of the source 36 in order to preventvoltage surges in the windings 28 when these latter are de-energized.

The operation is as follows: if the displacement takes place in thedirection L, the contacts 54 are connected as shown in FIG. 12. Assumingthat the windings 28a and 28b are excited, the excitation of thefollowing winding 280 is determined by the striking of the thyristor 510which is triggered by the gate 52c. This release occurs when thegenerator 53 delivers an impulse and the preceding winding 28b isexcited simultaneously. The striking of the thyristor 51c short-circuitsthe condenser 55a and thus creates a reverse potential at the terminalsof the thyristor 51a which becomes blocked. The winding 28a of the unit220 is no longer excited, while the winding 28c is put into circuit. Atthe following impulse, the thyristor 51d strikes and the thyristor 51bbecomes blocked and so on, the successive excitation of theelectromagnetic units 22 being effected in the direction L. In order toreverse the direction of movement, that is to say to effect it in thedirection M, it is only necessary to modify the position of the switch54 which changes the sequence of excitation of the second input of thegates 52. The diodes 56 protect the thyristors 51 against voltage surgeswhich may occur during the break of the corresponding circuit.

This electronic switch enables high powers to be controlled withaccuracy and avoids the problems presented by mechanical switches,especially the arcs due to voltage surges on interruption of inductivecircuits.

The checking of the control impulses can readily be made automatic inorder to ensure that the moving system has a movement at constant speedor at progressive acceleration, depending on the applications. For thispurpose, it is only necessary to control the impulse generator 53 independence on an appropriate parameter.

The electromagnetic device contemplated by the invention may, followinganother industrial application, be employed for the propulsion ofvehicles guided by a track for handling, transport of goods orpassengers. In particular, this device may equip railway vehicles,monorails or ground-effect vehicles.

In these applications, the magnetized assembly is preferably stationaryand follows the outline of the track. The electromagnetic units whichform the magnetizing assembly are mounted on the vehicle and aresupplied with electric current derived from any known means.

While in certain cases, especially of conveyors, it is necessary toprovide control means external to the vehicle, as in the machines whichhave been described in the preceding embodiments, in the present casethe control and in consequence the switching of the electromagneticunits is effected directly from the interior of the vehicle.

In the construction shown in FIGS. 13 to 16, there is indicateddiagrammatically at 60 the frame of a vehicle fitted with wheels 61 andmoving along a normal railway track 62. The fixed magnetized assembly 63which constitutes a rail and follows the outline of the track isarranged at equal distances from the two rails 62. The upper part of themagnetized assembly 63 comprises a succession of teeth 64, separated bynon-magnetic sections 65, produced very economically by simplecutting-out. A suitable magnetized assembly may be made from a normalcarbon steel of good quality.

The driving section is preferably constituted by several magnetizingassemblies distributed amongst the vehicles of a train. There is thusobtained a moving assembly having a small mass, which more readilyfollows the irregularities of profile of the magnetized assembly 63.Furthermore, this multiplication of the driving units results in abetter utilization of the magnetized assembly, pennits of manufacture ona larger scale and at low cost of small light driving units which arereadily housable in and removable from all the vehicles of a train, andprovides an installed power proportional to the size of the train.

In the particular construction described, the magnetizing assemblyprovided for a vehicle 60 comprises four electromagnetic units 67 fixedon a frame 66 mounted elastically in the lower part of the vehicle 60.Each unit 67 comprises a circuit 68 made from magnetic sheet, and twowindings 69 mounted on poles 71 defining an air-gap and arranged in suchmanner that the teeth 64 of the magnetized assembly 63 may pass in linethrough the abovementioned air-gap, perpendicular to the lines of forcebetween the poles 71, when the windings 69 are excited. The magneticcircuits 68 which are of C-shape are laminated in the plane of thislatter and are arranged at right angles to the direction 0 or N of themovement.

The non-magnetic frame 66 comprises enclosing flanges 70 and re-entrantflanges 72, which provide a housing for the circuits 68. This mountingreinforces the transverse rigidity of the assembly and offers remarkableresistance to the forces of attraction of the poles between each other.In particular, the flanges 70 which surround the base of the poles 71 ofeach magnetic circuit 68, preventing the bending of the sheets of thislatter due to the effect of the attraction force acting on the magneticteeth 64.

The frame 66 is fixed to the lower part of the vehicle 60 by means ofcrank-arms 73, mounted between elastic articulations 311, 312 (see FIG.15). The thrust or traction efforts of the magnetizing assembly aretransmitted to the vehicle 60 by at least one elastic coupling 74 whichdamps out the variations and the shocks of these efforts.

The guiding of the frame 66 with respect to the rail 63 is ensured bytwo pairs of rollers 75 mounted in opposition on each side of themagnetized rail 63, at the front and at the rear of the frame. Therollers 75 run just beneath notched portions 65 of the rail 63, and themechanical play is regulated in such manner that the distance betweenthe poles 71 and the magnetic teeth 64 is greater than at least twicethe value of the mechanical play. Thus, the attraction forces of thepoles are balanced and the residual lateral force is negligible. Asticking effect of the poles on the magnetized assembly is a fortio imade impossible. These mechanical and magnetic clearances and the wheelbase of the rollers 75 are determined in such manner that in curves ofshort radius, the pole surfaces 71 remain sufficiently distant from themagnetized assembly 63.

According to an improvement, the magnetized rail 63 also serves as athird rail for supplying current. For this purpose, it is insulated fromthe track by a nonconductive sole-plate 77. The current is taken-off byone or more collector shoes (not shown) supported on the lateral surfaceof the rail.

According to a further special feature of the invention, it is providedthat the four electromagnetic units of the driving assembly areassociated in pairs, 67a, 670 on the one hand and 67b, 67d on the other,in such manner that in each pair (FIG. 39) when one of theelectromagnetic units 67a comes opposite a magnetic section 64 of themagnetized assembly 63, the other unit 67c is facing a non-magneticsection 65. In addition, the distance between the pairs of associatedunits 67a, 67c is such that when the poles of one pair are locatedrespectively opposite a magnetic section 64 and a non-magnetic section65, the poles of the other pair are situated opposite the half of amagnetic section 64 and the half of a non-magnetic space 65.

The supply of current to the windings 69a 69d associated in pairs iseffected as shown in FIG. 16 by means of a two-phase current source 79of variable frequency, such as a Diesel electric generating set carriedby the train. The conductors 3130 of the same phase supply twoassociated windings 69a, 690, by means of two power diodes 78 connectedin opposition so that one of the associated windings is supplied at eachhalf-wave. The same arrangement is adopted for the second phase(conductors 311%). The source 79, associated if necessary with aphase-shifting system, is furthermore arranged in such manner that thephaseshift between the phase conductors 313a, 3l3b is 90.

Thus, the four electromagnetic units 67 of the magnetizing assemblybegin to be excited respectively at 90, 180, 270 and 360 of the cycle,and each one of them ceases its operation 180 later.

In addition, if the electromagnetic units 67 are excited following thesequence a, b, c, d, the vehicle 60 will be propelled in the direction0. If the excitation sequence is a, d, c, b, the movement will takeplace in the opposite direction N.

No other means for controlling the direction of displacement isnecessary, since if the first electromagnetic unit excited tends tocause the movement to start in the wrong direction (the case, forexample, of the unit d, whereas the movement is desired in the directionthe subsequent windings (b, c, d, a, etc. will correct this tendency andthe movement will continue in the desired direction. The control ofspeed can be effected by varying the frequency of the source 79, andespecially by increasing it as the train gathers speed.

According to another alternative form shown in FIG. 40, thedetermination of the direction of the speed is effected by means of afeeler 76 such as a magnetic or capacitive detector which controls thetriggers of the thyratrons 401 or of the thyristors forming part of theelectronic switching device 402 of the electromagnetic units 67, whenthelatter are supplied, for example, in accordance with FIG. 12.

The control is regulated in such manner that the release impulse isproduced at a suitable moment with respect to the relative forwardmovement of the tooth 64 nearest the magnetized assembly 63. When anacceleration is necessary, the release of the thyratrons or thyristorsreferred to above can be effected in phase advance. This variation ofphase can be obtained by any means known per se and forming part of theelectronic triggering system (and especially by a phase-shift stage403), or by mechanically displacing the feeler 76 with respect to thechassis 66. The deceleration of the vehicle is effected in a similarmanner by a phase delay. This deceleration is independent of theadhesion of the wheels. For this reason, the braking of the vehicle canbe made very effective, flexible and silent, and gives a greater degreeof safety.

Due to the high inductive impedance of the circuits, the increase anddecrease of the current in the magnetizing windings 69 is delayed withrespect to the beginning and the end of the electric impulse deliveredby the generator 79.

In order to compensate for the effects of this 'delay at high speeds,the invention provides for increasing with the speed the advance of thesetting of the instants of the beginning and end of the driving electricimpulse with respect to the relative positions of the poles 71 and theteeth 64 of the magnetized assembly.

This advance makes it possible to prevent the subsistence of amagnetizing field in the air-gap at the moment when the poles 71 areabout to pass beyond the tooth 64 considered of the magnetized assembly63. in an arrangement of this kind, the feeler 76 may operate as aspeed-detection device and may permit the frequency modulation of asignal which is employed for the regulation of the phase between theimpulse periods and the instants when the magnetizing and magnetizedassemblies occupy pre-determined relative positions.

The reluctance of the magnetic circuit of the units 67 varies accordingto the displacement of the magnetizing assembly. According to a furtherparticular feature of the invention, it is then provided to adapt thislaw of variation to the most probable speed of the vehicle in thesection of track considered. The modifications of this law of variationmay be obtained by acting on the longitudinal profile of the magneticsections 64, on their thickness and on their magnetic characteristics.

In particular, provision is preferably made on the portions of trackintended for high speeds, for the formation of teeth such as 64a (FlG.13) of which at least the leading edge forms an acute angle with thedirection of movement, and the mean length of which is greater than forlow speeds, while the permeability and thickness are reduced.

These arrangements considerably reduce shocks and vibrations, andincrease the effort developed.

The method of propulsion of guided vehicles thus provided by theinvention may be advantageously applied to wall-effect vehicles andespecially to those of the air-cushion type. An application of thistype, shown in FIGS. 17 to 19, is advantageous since vehicles of thekind considered have no physical contact with the wall, so that it isdifficult for them to utilize the adhesion effect with the wall foracceleration or braking.

in this embodiment, the vehicle 80 is supported above an area 81 servingas a track by the ground effect resulting from air cushions 82 suppliedby distribution channels 83. The vehicle is guided by a vertical rib 84which forms the magnetized assembly with the magnetic sections 85 andthe non-magnetic sections 86 uniformly spaced apart. The magneticsections 85 are in this case constituted by parallelepiped blocks ofmagnetic material embedded in the guiding rib 84 of a non-magneticmaterial such as concrete. There is thus formed a low-cost magnetizedassembly which furthermore plays an essential part in guiding thevehicle along the track.

The magnetizing assembly 87 comprises, in this example, fourelectromagnetic units each comprising a magnetic circuit 88 in the formof a C, which has an airgap defined by the poles 91.

The windings 89 are mounted in pairs on each magnetic circuit 88 closeto he poles 91, in order to concentrate the magnetizing field in theair-gap, to reduce the leakage flux and to have the maximum drivingforce on each magnetic section for a given magneto-motive force.

The guiding of the magnetizing assembly 87 is effected by the walleffect resulting from air cushions 94 created between the rib 84 and thesaid assembly. The cushions 94 are supplied through channels 93,depending on the size of the vehicle.

1. A transporter system comprising at least one beam serving as a track,at least one car suspended from and movable along said track andprovided with drive means for imparting motion thereto, said drive meanscomprising a magnetizing assembly and and a magnetized assembly adaptedto move one with respect to the other and mounted one on said beam andthe other on said car, the magnetizing assembly comprising a pluralityof electromagnetic units disposed in line and each said unit comprisingone magnetic circuit having two oppositely facing pole faces defining anair gap therebetween and having at least one inductor winding, themagnetized assembly projecting into said air gap in the magnetic fieldof the magnetizing assembly and comprising a plurality of magneticsections disposed in line in alternate relation with non-magneticsections, each said magnetic section comprising at least a pair ofoppositely facing surfaces, at least a pair of said section surfacesfacing respectively two of the said pole faces of a said magneticcircuit so that the magnetic flux generated by said inductor winding andacting upon said magnetic section enters one of said section surfacesand leaves the opposite surface of said magnetic section, the pitch ofsaid magnetic sections being different from that of the electromagneticunits of said magnetizing assembly, switching means for supplyingcurrent pulses to the windings of said electromagnetIc units accordingto a predetermined sequence, each pulse of the sequence being suppliedat about the time when one of the magnetic sections reaches the entranceof the corresponding air gap, means for guiding the relativedisplacement of the said magnetized assembly through the air gaps ofsaid electromagnetic units in a direction crossing the lines of forcewithin said air gaps, the direction of said lines of force beingsubstantially the same in said air gaps and in said magnetic sections ofsaid magnetized assembly, sensing means for detecting a parameter ofthat assembly which is moving with respect to the other assembly, andmeans controlled by said sensing means for controlling the currentpulses supplied to said windings.
 2. A system as claimed in claim 1,said sensing means detecting the position of said moving assembly.
 3. Asystem as claimed in claim 1, said sensing means detecting the speed ofsaid moving assembly.
 4. A system as claimed in claim 1, said sensingmeans detecting the direction of movement of said moving assembly.
 5. Asystem as claimed in claim 1, said controlling means controlling thebeginning of the current pulses.
 6. A system as claimed in claim 1, saidcontrolling means controlling the end of said current pulses.
 7. Asystem as claimed in claim 6, said means controlling the end of thecurrent pulses effecting the interruption of a current pulse fed to anelectromagnetic unit before the corresponding magnetic section reaches acentral position in the corresponding air gap.
 8. A system as claimed inclaim 1, said controlling means controlling the order in which saidcurrent pulses are supplied to said windings.
 9. A system as claimed inclaim 1, the line in which said electromagnetic units are disposed beinga straight line.
 10. A system as claimed in claim 1, the line in whichsaid electromagnetic units are disposed being a curved line.
 11. Asystem as claimed in claim 1, the amount by which the pitch of saidmagnetic sections is different from that of the electromagnetic units ofsaid magnetizing assembly being such that the axial length of N pitchesof one said assembly is equal to the length of (N+1) pitches of theother assembly, N being a whole number.
 12. A system as claimed in claim1, said guiding means being so arranged that the mechanical play of saidmagnetized assembly in a direction parallel to the lines of force withinthe air gaps of said electromagnetic units is substantially less thanthe value of the residual air gap between the pole faces of said unitsand the oppositely facing surfaces of the magnetic sections of saidmagnetized assembly when the latter are in the position of minimumreluctance.
 13. A transporter system comprising at least one memberserving as a track, at least one member movable along said track andprovided with driving means for imparting motion thereto, said drivingmeans comprising a magnetizing assembly and a magnetized assembly, oneof said assemblies being carried by one of said members and the other ofsaid assemblies being carried by the other of said members, themagnetizing assembly comprising a plurality of electromagnetic unitsdisposed in line and each said unit comprising one magnetic circuithaving two oppositely facing pole faces defining an air gap therebetweenand having at least one inductor winding, the magnetized assemblyprojecting into said air gap in the magnetic field of the magnetizingassembly and comprising a plurality of magnetic sections disposed inline in alternate relation with non-magnetic sections, each saidmagnetic section comprising at least a pair of oppositely facingsurfaces, at least a pair of said section surfaces facing respectivelytwo of the said pole faces of a said magnetic circuit so that themagnetic flux generated by said inductor winding and acting upon saidmagnetic section enters one of said section surfaces and leaves theopposite surface of said magnetic section, the pitch of said magneticseCtions being different from that of the electromagnetic units of saidmagnetizing assembly, switching means for supplying current pulses tothe windings of said electromagnetic units according to a predeterminedsequence, each pulse of the sequence being supplied at about the timewhen one of the magnetic sections reaches the entrance of thecorresponding air gap, means for guiding the relative displacement ofthe said magnetized assembly through the air gaps of saidelectromagnetic units in a direction crossing the lines of force withinsaid air gaps, the direction of said lines of force being substantiallythe same in said air gaps and in said magnetic sections of saidmagnetized assembly, sensing means for detecting a parameter of thatassembly which is moving with respect to the other assembly, and meanscontrolled by said sensing means for controlling the current pulsessupplied to said windings.
 14. A system as claimed in claim 13, saidsensing means detecting the position of said moving assembly.
 15. Asystem as claimed in claim 13, said sensing means detecting the speed ofsaid moving assembly.
 16. A system as claimed in claim 13, said sensingmeans detecting the direction of movement of said moving assembly.
 17. Asystem as claimed in claim 13, said controlling means controlling thebeginning of the current pulses.
 18. A system as claimed in claim 13,said controlling means controlling the end of said current pulses.
 19. Asystem as claimed in claim 18, said means controlling the end of thecurrent pulses effecting the interruption of a current pulse fed to anelectromagnetic unit before the corresponding magnetic section reaches acentral position in the corresponding air gap.
 20. A system as claimedin claim 13, said controlling means controlling the order in which saidcurrent pulses are supplied to said windings.
 21. A system as claimed inclaim 13, the line in which said electromagnetic units are disposedbeing a straight line.
 22. A system as claimed in claim 13, the line inwhich said electromagnetic units are disposed being a curved line.
 23. Asystem as claimed in claim 13, the amount by which the pitch of saidmagnetic sections is different from that of the electromagnetic units ofsaid magnetizing assembly being such that the axial length of N pitchesof one said assembly is equal to the length of (N+1) pitches of theother assembly, N being a whole number.
 24. A system as claimed in claim13, said guiding means being so arranged that the mechanical play ofsaid magnetized assembly in a direction parallel to the lines of forcewithin the air gaps of said electromagnetic units is substantially lessthan the value of the residual air gap between the pole faces of saidunits and the oppositely facing surfaces of the magnetic sections ofsaid magnetized assembly when the latter are in the position of minimumreluctance.
 25. A system comprising guide means, means movable on saidguide means, drive means for imparting motion to said movable means onsaid guide means, said motion-imparting means comprising anelectromagnetic device producing a mechanical action and comprising amagnetizing assembly and a magnetized assembly adapted to move one withrespect to the other, one of said assemblies being carried by said guidemeans and the other of said assemblies being carried by said movablemeans, the magnetizing assembly comprising a plurality ofelectromagnetic units disposed in line and each said unit comprising onemagnetic circuit having two oppositely facing pole faces defining an airgap therebetween and having at least one inductor winding, themagnetized assembly projecting into said air gap in the magnetic fieldof the magnetizing assembly and comprising a plurality of magneticsections disposed in line in alternate relation with non-magneticsections, each said magnetic section comprising at least a pair ofoppositely facing surfaces, at least a pair of said section surfacesfacing respectively tWo of the said pole faces of a said magneticcircuit so that the magnetic flux generated by said inductor winding andacting upon said magnetic section enters one of said section surfacesand leaves the opposite surface of said magnetic section, the pitch ofsaid magnetic sections being different from that of the electromagneticunits of said magnetizing assembly, switching means for supplyingcurrent pulses to the windings of said electromagnetic units accordingto a predetermined sequence, each pulse of the sequence being suppliedat about the time when one of the magnetic sections reaches the entranceof the corresponding air gap, said guide means guiding the relativedisplacement of the said magnetized assembly through the air gaps ofsaid electromagnetic units in a direction crossing the lines of forcewithin said air gaps, the direction of said lines of force beingsubstantially the same in said air gaps and in said magnetic sections ofsaid magnetized assembly, sensing means for detecting a parameter ofthat assembly which is moving with respect to the other assembly, andmeans controlled by said sensing means for controlling the currentpulses supplied to said windings.
 26. A system as claimed in claim 25,said sensing means detecting the position of said moving assembly.
 27. Asystem as claimed in claim 25, said sensing means detecting the speed ofsaid moving assembly.
 28. A system as claimed in claim 25, said sensingmeans detecting the direction of movement of said moving assembly.
 29. Asystem as claimed in claim 25, said controlling means controlling thebeginning of the current pulses.
 30. A system as claimed in claim 25,said controlling means controlling the end of said current pulses.
 31. Asystem as claimed in claim 30, said means controlling the end of thecurrent pulses effecting the interruption of a current pulse fed to anelectromagnetic unit before the corresponding magnetic section reaches acentral position in the corresponding air gap.
 32. A system as claimedin claim 25, said controlling means controlling the order in which saidcurrent pulses are supplied to said windings.
 33. A system as claimed inclaim 23, in which the residual air gap between the pole faces of saidelectromagnetic units and the oppositely facing surfaces of the magneticsections of said magnetized assembly is at least equal to twice themaximum mechanical play of said magnetized assembly in a directionparallel to the lines of force within the air gaps of saidelectromagnetic units.
 34. A system as claimed in claim 25, in which thesection of passage of the magnetic flux in the magnetic circuits of saidelectromagnetic units and in the magnetic sections of said magnetizedassembly is determined in such a way that said magnetic sections aresaturated before said magnetic circuits reach saturation.
 35. A systemas claimed in claim 25, in which the moving assembly is mounted belowthe fixed assembly and is suspended by magnetic attraction, retentionmeans being further provided for preventing said moving assembly fromfalling in case of interruption of current supply to said magnetizedassembly.
 36. A system as claimed in claim 25, in which saidelectromagnetic units of the magnetizing assembly are connected inparallel to a single source of electrical energy through means fordifferential regulation of the voltage across the terminals of thewindings of said electromagnetic units, said means comprisingsynchronized sliders and means for controlling the displacement of saidsliders in dependence of the desired position of the moving assembly.37. A system as claimed in claim 25, the line in which saidelectromagnetic units are disposed being a straight line.
 38. A systemas claimed in claim 25, the line in which said electromagnetic units aredisposed being a curved line.
 39. A system as claimed in claim 25, theamount by which the pitch of said magnetic sections is different fromthat of the electromagnetic units of said magnetiZing assembly beingsuch that the axial length of N pitches of one said assembly is equal tothe length of (N+1) pitches of the other assembly, N being a wholenumber.
 40. A system as claimed in claim 25, said guiding means being soarranged that the mechanical play of said magnetized assembly in adirection parallel to the lines of force within the air gaps of saidelectromagnetic units is substantially less than the value of theresidual air gap between the pole faces of said units and the oppositelyfacing surfaces of the magnetic sections of said magnetized assemblywhen the latter are in the position of minimum reluctance.